* the {@code ForwardingConcurrentMap}.
 *
 * @author Charles Fry
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingConcurrentMap<K, V> extends ForwardingMap<K, V>
    implements ConcurrentMap<K, V> {

  /** Constructor for use by subclasses. */
  protected ForwardingConcurrentMap() {}

  @Override
  protected abstract ConcurrentMap<K, V> delegate();

 * the {@code ForwardingConcurrentMap}.
 *
 * @author Charles Fry
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingConcurrentMap<K, V> extends ForwardingMap<K, V>
    implements ConcurrentMap<K, V> {

  /** Constructor for use by subclasses. */
  protected ForwardingConcurrentMap() {}

  @Override
  protected abstract ConcurrentMap<K, V> delegate();

   * circular dependency is present, so the proxy must be able to behave as the map itself.
   */
  abstract static class AbstractSerializationProxy<K, V> extends ForwardingConcurrentMap<K, V>
      implements Serializable {
    private static final long serialVersionUID = 3;

    final Strength keyStrength;
    final Strength valueStrength;